1. Field of the Invention
The present invention relates generally to methods for using dental compositions containing polymerizable resins and fluorescent compounds. The dental compositions can be used as flowable composites (fillings), adhesives, sealants, and the like. The dental compositions are preferably used as dental sealants.
2. Brief Description of the Related Art
Dental professionals apply a sealant to the surface of a tooth in order to provide long-term protection against dental caries, which is caused by the accumulation of bacteria. The bacteria in plaque produce acids that eat into the tooth, eventually causing cavities to form therein. Pits and fissures may develop in the surface of a tooth, and bacteria tend to accumulate in these areas. Sealants are commonly used to fill the pits and fissures in the surface of a tooth, particularly the occlusal surfaces of posterior teeth. The sealants, once applied and cured, provide a smooth seal and prevent the ingress of fluids, food, and debris. The sealant can either have a clear composition or opaque composition to match the color of the tooth. Both types of sealant compositions tend to have a glossy surface finish and provide an aesthetically-pleasing appearance.
The dental professional must apply the sealant carefully so that it completely seals the pits and fissures in the surface of the tooth. Typically, the sealant is applied with a brush or other applicator. Then, the sealant is cured and hardened. The curing step normally involves irradiating the sealant with blue visible light having a wavelength generally in the range of about 400 to about 700 nm. The application and curing of the sealant can be difficult. When a clear sealant composition is used, the dentist may have trouble discerning between the pits and fissures, which need to be sealed, versus healthy dentition. It also can be difficult to apply an opaque sealant composition, because the color of the sealant composition and natural color of the tooth can be substantially the same. Another problem with some conventional sealants is that they tend to wear-away over time. When the dentist examines the patient in follow-up visits, he or she may not be able to easily detect if portions of the sealant have worn off. As part of an effort to address these problems, the dental industry has developed dental sealants containing fluorescing compounds. With these fluorescing sealants, the dental professional is better able to check margins and determine if the sealant has been placed accurately on the surface of the tooth during initial patient visits. In follow-up visits, the dentist can examine the patient's tooth, under fluorescing conditions, to determine if the sealant has worn off.
For example, Schwartz, U.S. Pat. No. 4,600,389 discloses dental compositions used for making restorations, inlays, onlays, crowns, sealants, glazes, and cements. The composition contains microbeads having a fluorescent rare earth chelated compound therein. The fluorescent rare earth compound is permanently isolated within the microbeads. The composition is colorless when viewed under ordinary daylight, sunlight, or disco light but is highly fluorescent when exposed to ultraviolet radiation having a wavelength of 300 to 400 nm according to the '389 patent.
Rheinberger et al., U.S. Pat. No. 5,102,461 relates to a colorless dental material that can be distinguished from natural teeth, false teeth, and other dental materials. The colorless dental material includes a fluorescent substance that emits fluorescent light as a result of being irradiated with radiation having a wavelength in the region of 360 to 480 nm. Suitable dental materials, which, can be made in accordance with the '461 patent, include spacer varnishes, blocking materials, composite filling materials, cements, and sealants. The dental material is irradiated with light having a wavelength in the region of 360 to 480 nm, and the material is viewed through a light filter. The '461 patent teaches that the interfering effects caused by reflection of the irradiating light (360 to 480 nm) and the natural fluorescence of teeth are overcome by using the light filter.
Robinson et al., U.S. Pat. No. 5,211,748 discloses a dental restorative composition containing an additive that fluoresces under radiation having a wavelength in the visible light spectrum. The preferred additive is chromium-activated “crushed ruby.” According to the '748 patent, a conventional light source, such as a blue light used for curing dental composites, can be used to irradiate the composition with the required visible light. The ruby additive fluoresces when irradiated by visible-wavelength light but does not fluoresce when irradiated by ultra-violet light.
Although some of the foregoing dental compositions can be used effectively as dental sealants, there is still a need for an improved composition. It would be particularly desirable to use a fluorescent compound, which does not impart any substantial color to the composition. The sealant, containing the fluorescent compound, would maintain its ordinary color after it had been applied to the surface of the tooth and while it was in an uncured condition. The sealant would maintain this same color after it had been cured. It also would be desirable to have a composition, which would fluoresce upon being irradiated with ultraviolet light, but would revert quickly to its ordinary color when it was no longer exposed to the ultraviolet light. The present invention provides a dental sealant having these desirable properties as well as other features and advantages.